Vibrating ball mill having baffle plate for increasing retention time of material in mill



Dec. 31, 1957A G. v. wooDY 2,818,220

VIBRATING BALL MILL HAVING BAFFLE PLATE FOR INCREASING RETENTION TIME OFMATERIAL IN MILL Filed Oct. 14, 1954 du vanYo United States PatentVIBRATNG BALL MILL HAVING BAFFLE PLATE FR INCREASING RETENTION TlME 0FMATE- REAL IN Mill.

Guy V. Woody, Milwaukee, Wis., assignor to Alli.,- ChaimersManufacturing Company, Milwaukee, Wis.

Application October 14, 1954, Serial No. 462,298

4 Claims, (Cl. 241--175) mill for performing Wet grinding operations,that is, the

grinding of materials in the presence of a liquid.

The wet grinding of materials as contemplated herein includes (l) thereducing by grinding of mineral ores or other solid materials held insuspension in a liquid to more or less finely granulated particles, and(2) the grinding of oleaginous materials of cellular character such aslinseed, cottenseed and soybean in the presence of a liquid such as asolvent, water or an aqueous solution, the grinding of the materialbeing effective to crush, rupture, press, cut or break the oil cells ofthe material .to expose or displace the oil so as to permit the oil tocombine with the liquid.

With a continuous grinding operation, as distinguished from a batchoperation, the wet grinding of materials involves the continuous feedingof a slurry of the material to be ground to a vibrating ball mill and acontinuous discharge of a slurry of material from the mill. In practicea complete or finished grinding operation is effected by recirculatingthrough the mill a portion of the material discharged because in manycases, if the material is passed through the mill only once, theretention v .time of the material in the mill is not sufiicient for thematerial to be ground to the desired fineness. The recirculating of thematerial may involve a separating operation in which material which hasnot been suficiently ground is isolated and returned to the feed openingof the mill or, more simply, merely returning a portion of thedischarged material to the mill without a separating operation. lneither case, the recirculated material is continuously supplemented witha fresh slurry of material .to comprise the material which iscontinuously fed to the mill.v

v In wet grinding operations of the type referred to, the longer thematerial is retained in the mill before it is discharged, the greater isthe opportunity for the material to be acted upon and reduced to thedesired degree by the grinding balls. lt is to this end that the"present invention is directed.

In accordance with the present invention a vibrating type ball mill isprovided having bathe means for increasing the retention time in themill of the material passing through the mill. The baffle means alsofunctions to prevent portions of material passing through the mill fromtaking the shortest route from the feed opening to the dischargeopening. The advantage of this latter function is that the dischargingfrom the mill of substantially unground portions of material is avoided.An object of the present invention is to provide a new and improvedvibrating type ball mill for continuous wet grinding operations in whichthe retention time in the "ice creased. Another object, which isrealized by increasing the retention time, is to increase the effectivecapacity of the mill in terms of the amount of material ground to thedesired size per hour.

Another object of the invention is to prevent portion of the materialpassing through the mill from taking the shortest route from the feedopening to the discharge opening.

Another object of the invention is to provide a vibrating type ball millin which grinding bodies of different sizes may be segregated so thatlarger grinding bodies are effective to grind material at the feed endof the mill and smaller grinding bodies are effective to grind materialat the discharge end of the mill to provide an efficient grindingoperation.

rOther objects will become apparent from the following detaileddescription of the invention and the accompanying drawing which showsone embodiment of th invention.

In the drawing:

Fig. 1 is a vertical sectional view through the longitudinal axis of avibrating ball mill embodying the present invention; and

Fig. 2 is a cross sectional view taken on line lI-l-l of f lFig. l.

Referring to Figs. l and 2, a suitably shaped container liti,illustrated as having a cylindrical shape and havin-g end walls 1l and12 is suspended by cables 13 from ya stationary overhead supportingstructure ld. Resilient means such as springs are provided betweencables 13 and supporting structure 14 to allow container lt) to have avibrational movement relative to supporting structure 11.4.

End walls l1 and l2 are provided with suitably positioned bearinghousings and 2i in which bearings 22 and 23 are mounted. As illustratedherein bearings Z2 and 23 are in coaxial relation to the longitudinalaxis 24 of container lil. Rotatably journaled in bearings 22 and 23 is ashaft 25 with the axis thereof being coincident with the longitudinalaxis 24 of container lil. Suitable sealing means and 31 are provided,respectively, between shaft 25 and bearing housings 20 and 21. Aprotective tube 26 which surrounds shaft 25 and extends between walls iland l2 of container l0 may be provided.

Weight means 312. and 33 are rigidly attached at opposite ends of shaft25, preferably in phase with each other, and each of the weight meanshas a center of mill of the slurry of material fed to the mill isingravity disposed eccentrically of the axis of shaft 25 and thelongitudinal axis 24 of container lll. Upon rotating shaft Z5 thecentrifugal forces imparted to shaft 25 by weight means 32 yand 33 aretransmitted through bearings 22 and 23 so as -to cause container 1S tovibrate.

A motor 34 mounted on a stationary support 3a' is provided for drivingshaft Z5 of the vibrating bali mill. As the container 1d of the mill isvibrat'able relative to motor 34, a flexible coupling 36 is providedbetween shaft itl of the motor and shaft 25 of the mill.

A feed inlet al at the top at one end of container lil and a dischargeoutlet 42 at the bottom at the opposite end of container iti areprovided. Means for feeding a slurry of the material to be ground to themill such as a hopper 413 is also provided and a slurry of material tobe ground is continuously fed to the mill through inlet il and a slurryof ground material is continuously withdrawn from the mill throughdischarge opening 42.

A baffle plate 45 for increasing the retention time of material passingthrough the mill is provided. Baffie plate 45 extends transversely ofthe axis of the mill and is mounted in the lower portion of the millwith the upper edge thereof being between the horizontal center line ofthe mill and the top of the mill. Baie plate 45 may be asiaaeo suitablypositioned approximately one-third the length of container from wall 11thereof.

When the mill is in operation, the ball charge and the material beingground revolves as a whole in a direction opposite the direction ofgyration of container lt). Referring to Fig. 2, the gyratory movement ofthe container 1G is indicated as countercloclrwise and the revolvingmovement of the ball charge and material is indicated as clockwise.

As seen in Fig. 2, during operation of the mill the upper left portionof container 10 is not contacted by the ball charge and the material. Ifdesired, the partition t5 may therefore be formed, as shown in Fig. 2,with the upper edge thereof disposed at an angle of about relative to ahorizontal plane through the axis of the mill.

Material to be ground or otherwise acted upon by the ball charge, whichcomprises grinding bodies 4o, enters feed inlet 41 in the form of aslurry and flows to the enclosure 47 to the left of baille plate 45. Thematerial is subjected to the grinding action of the ball charge While itis retained in the enclosure 47. As there is a continuous stream ofmaterial entering through feed inlet 4l, a slurry of partially groundmaterial continuously overflows baffle plate 45 into enclosure 43 wherethe material is subjected to further grinding action of the ball chargebefore being discharged through outlet 42.

A perforated discharge diaphragm or head 49 is positioned near dischargeoutlet 4Z, the perforations therein being large enough to allow theslurry of material to pass freely therethrough but small enough toprevent the escape of the grinding bodies 46.

ln addition to delaying the flow of the slurry of material through themill, that is, increasing the retention time, baffle plate 45 preventsportions of material from taking the shortest route through the millfrom the feed inlet 41 to the discharge outlet 42. All of the materialentering the mill is caused by baffle plate 45 to take a more or lesscircuitous path before being discharged and all of the material owingthrough the mill is thereby retained in the mill long enough to receiveconsiderable grinding treating.

A main function of the baffle plate 45 is to prevent oversized particlesfrom passing through the mill without being suiliciently acted upon bythe grinding balls. Small perforations in the baflle plate which allowsmaller sized particles to pass therethrough may therefore be toleratedwithout materially affecting the functioning of the baffle plate.

ln a wet grinding operation, apparatus not shown is provided forrecirculating through the mill a portion of the material dischargedthrough outlet d2. An overall advantage obtained with the use of thepresent invention is that a considerably lesser portion can berecirculated without sacrificing the degree of fineness to which the endproduct of the mill is ground or reduced. The reason is that the bailleplate 45' causes the material to take longer to flow through the mill sothat there is greater opportunity for the grinding balls to act on thematerial and, further, portions of material are not allowed to bedischarged from the mill without being subjected to a substantialgrinding action.

Another advantage which may be obtained with the use of the presentinvention is that large and small grinding balls may, if desired, besegregated to obtain a more efficient grinding operation. lf one inchand one-half inch balls are utilized, for example, the one inch ballsmay be disposed to the left of baffle plate 45 at the feed end of themill and the one-half inch balls may be disposed to the right of bafeplate 45 at the discharge end of the mill. Suitable grating (not shown)or the like could be provided above the upper edge of bale plate 45which would allow material being ground to flow over the baffle platebut would prevent the segregated grinding balls from doing so. With thisarrangement the material to be ground first comes into contact with thelarger balls at the feed end of the mill and the relatively largerpieces of material are reduced in size. When the material flows overbafe plate 45 and comes in contact with the smaller balls a linergrinding of the material is effected. With this arrangement the largergrinding balls act upon the large particles of the material being groundand the smaller grinding balls act upon the smaller partially groundparticles to provide a very eiicient grinding operation.

While only one embodiment of the invention is described and illustratedherein, it is to be understood that other embodiments and modications ofthe invention may be made and used Without departing from the spirit andscope of the invention as set forth in the appended claims.

l t is claimed and desired to secure by Letters Patent:

l. A vibrating type ball mill for continuous wet grinding operationscomprising a container with a substantially horizontally disposedlongitudinal axis and an arcuately formed bottom portion, said containerbeing adapted to be supported for gyratory movement transversely of itsaxis for advancing material to be ground through said container along agenerally spiral path relative to said container axis, an inlet openingdisposed at one end of said container at the top thereof and a dischargeopening disposed at the other end of said container at the bottomthereof, and a baffle plate for increasing the retention time ofmaterial passing through the mill extending transversely of said axis inthe lower portion of said container and positioned intermediate saidinlet and discharge openings, said baffle plate having a continuousupper edge inclined upwardly in the direction of the transversecomponent of the generally spiral path of material flow relative to saidcontainer.

2. A vibrating type ball mill for continuous wet grinding operationscomprising a container with a substantially horizontally disposedlongitudinal axis and an arcuately formed bottom portion, said containerbeing adapted to be supported for gyratory movement transversely of itsaxis for advancing material to be ground through said container along agenerally spiral path relative to said container axis, a feed openingdisposed at one end of said container at the top thereof and a dischargeopening disposed at the other end of said container at the bottomthereof, and a baffle plate for increasing the retention time ofmaterial passing through the mill extending transversely of said axis inthe lower portion of said container and positioned intermediate saidinlet and discharge approximately one-third the length of said containerfrom the feed end thereof, said baffle plate having a continuous upperedge inclined upwardly in the direction of the transverse component ofthe generally spiral path of material ow relative to said container.

3. A vibrating type ball mill for continuous wet grinding operationscomprising a container with a substantially horizontally disposedlongitudinal axis and an arcuately formed bottom portion, said containerbeing adapted to be supported for gyratory movement transversely of itsaxis for advancing material to be ground through said container along agenerally spiral path relative to said container axis, a shaft iournaledin said container concentrically with said axis and having eccentricweight means associated therewith for imparting a gyratory movement tosaid container, a cylindrical casing disposed in said container andsurrounding said shaft in concentric relation thereto, an inlet openingdisposed at one end of said container at the top thereof and a dischargeopening disposed at the other end of said container at the bottomthereof, and a baffle plate for increasing the retention time ofmaterial passing through the mill extending transversely of said axis inthe lower portion of said container and positioned intermediate saidinlet and discharge openings, said baffle plate having a continuousupper edge inclined upwardly in the direction of the transversecornponent of the generally spiral path of material ilow re1- ative tosaid container.

4. A vibrating type ball mill for continuous wet grinding operationscomprising a container with a substantially horizontally disposedlongitudinal axis and an arcuately formed bottom portion, said containerbeing adapted to be supported for gyratory movement transversely of itsaxis for advancing material to be ground through said container along agenerally spiral path relative to said container axis, an inlet openingdisposed at one end of said container at the top thereof and a dischargeopening disposed at the other end of said container at the bottomthereof, and a baffle plate positioned intermediate said inlet anddischarge openings for increasing the retention time of material passingthrough the mill which extends transversely of said axis in the lowerportion of said container and has a continuous upper edge at an angle ofabout 15 degrees relative to a horizontal plane and the inclination ofsaid edge being upwardly in the direction of the transverse component ofthe generally spiral path ot material flow relative to said container. 5

References Cited in the le of this patent UNITED STATES PATENTS 926,441Shatter June 29, 1909 10 983,069 Lindhard Jan. 31, 1911 2,019,454 LarsenOct. 29, 1935 2,208,077 Linke July 16, 1940 2,298,015 Lincoln Oct. 6,1942 FOREIGN PATENTS 15 685,226 Germany Dec. 14, 1939

